Is there any buddhist meditation technique to connect to Nature?

The Buddha normally practiced the meditation on emptiness:

MN121:3.3: ‘Ānanda, these days I usually practice the meditation on emptiness.’

This is a very deep practice that starts with the Sangha as the entry to emptiness:

MN121:4.2: There is only this that is not emptiness, namely, the oneness dependent on the mendicant Saṅgha.

And from that we proceed to wilderness (i.e., "Nature"):

MN121:4.3: In the same way, a mendicant—ignoring the perception of the village and the perception of people—focuses on the oneness dependent on the perception of wilderness.
MN121:4.4: Their mind becomes eager, confident, settled, and decided in that perception of wilderness.

From there it goes much further...

About two summers ago, I was walking through the local farmland and I noticed a very big bird coming in for a landing in the middle of the farmer's field. I watched it like a zen master, taking in the entirety of the visual spectacle, and then I wrote this. I’d rather not explain what this means in zen terms; the air of ambiguity is important when reading zen text.

The Heron Called Dogen: The heron stands tall, firm and erect, proud to claim the visual vastness of the farmer’s land, its abundant fruits, and its majesty of gently rustling crops breaking the silent theme of the countryside. Not looking back once, it flies away unattached, leaving not a single plough in the sky.

Zen master Hongzhi (who appears to have some amazing eyebrows!) had a wonderful thing about using the nowness of nature, which is why I liked his work so much and is largely where I started. I believe at one point in his life, he brushed shoulders with Dogen and they shared various exchanges. It was studying his material where I learned how to watch nature. In fact, I'm pretty sure Hongzhi’s works are elementally foundational in the entire Caodong school, itself.

In any case, my relationship with nature developed further -

15. Stillness

Over there in the far distance, beyond the rustling trees and the meadow with the flowers, barely audible... the stream trickles.

Over here in the body, beyond the mental chatter and the colourful tints of perception, barely noticeable... the blood flows.

Attend there.

And then finally -

Who was the outstanding artist that built this old, dishevelled brick wall, laden with bird shit, graffiti tags and wisteria? Was it the mindless bricklayer, the time-honoured weather, the graffiti artist or the slow-moving foliage? It was a collaborative effort between all creation, and precisely why it doesn't stand out from anything else is precisely why I'm stood here laughing at this brick wall!

Suffice to say, I became somewhat of a savant with it all, until eventually, even the horrors of the woeful realms became like the tomfoolery of nature!

For this reason, in Zen there is a deep respect for the parameters of language and to know that respect is to know the nature of Zen as it stands, naked of language, in the here-and-now.

The Buddha didn't talk about a cosmic consciousness, but he did advocate meditating outdoors.

From Mindfulness of Breathing - MN 118

"...It’s when a mendicant has gone to a wilderness, or to the root of a tree, or to an empty hut. They sit down cross-legged, with their body straight, and establish mindfulness right there. Just mindful, they breathe in. Mindful, they breathe out..."

From MN 107 which is on The Gradual Training

"...When they have mindfulness and situational awareness, the Realized One guides them further: ‘Come, mendicant, frequent a secluded lodging—a wilderness, the root of a tree, a hill, a ravine, a mountain cave, a charnel ground, a forest, the open air, a heap of straw.’ And they do so..."

Seclusion is not about harmonizing with nature, but being in the wilderness is a good way to avoid people.

You’ve unwittingly stumbled upon the answer to one particularly well known koan. I’m not going to tell you which one it is because it won’t necessarily help you. But be advised that what you encountered is real. File it away in your back pocket for now and try not to cling to it.

Our practice mainly consists of partial insights like this. They are bricks knocked out of the wall between us and awakening. While the light that shines through is real, it’s not the full illumination no matter how bright it might first appear. There’s a real danger when we attach too much importance to partial insights. All too often we get stuck - clinging to this incomplete knowledge. We might also weave philosophical interpretations that can stymy our practice for years.

There’s are more koans to come, more insights to be had, and dharma gates beyond measure. Put this down and keep going!

There's no Cosmic Consciousness in Buddhism. Any consciousness that we have, depends on the six senses alone.

The Blessed One said, "What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All. Anyone who would say, 'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range."
SN 35.23

However, the closest meditation on nature that I can find is the following by the Zen Master Thich Nhat Hahn from the article "The Heart Sutra: The Fullness of Emptiness":

If you are a poet, you will see clearly that there is a cloud floating in this sheet of paper. Without a cloud, there will be no rain; without rain, the trees cannot grow; and without trees, we cannot make paper. The cloud is essential for the paper to exist. If the cloud is not here, the sheet of paper cannot be here either. We can say that the cloud and the paper inter-are. “Interbeing” is a word that is not in the dictionary yet, but if we combine the prefix “inter-” with the verb “to be,” we have a new verb, “inter-be.”

If we look into this sheet of paper even more deeply, we can see the sunshine in it. If the sunshine is not there, the forest cannot grow. In fact, nothing can grow. Even we cannot grow without sunshine. So we know that the sunshine is also in this sheet of paper. The paper and the sunshine inter-are. And if we continue to look, we can see the logger who cut the tree and brought it to the mill to be transformed into paper. And we see the wheat. We know that the logger cannot exist without his daily bread, and therefore the wheat that became his bread is also in this sheet of paper. And the logger’s father and mother are in it too. When we look in this way, we see that without all of these things, this sheet of paper cannot exist.

Looking even more deeply, we can see we are in it too. This is not difficult to see, because when we look at a sheet of paper, the sheet of paper is part of our perception. Your mind is in here and mine is also, so we can say that everything is in here in this sheet of paper. You cannot point out one thing that is not here — time, space, the earth, the rain, the minerals in the soil, the sunshine, the cloud, the river, the heat. Everything coexists with this sheet of paper. That is why I think the word inter-be should be in the dictionary. To be is to inter-be. You cannot just be by yourself alone. You have to inter-be with every other thing. This sheet of paper is, because everything else is. Suppose we try to return one of the elements to its source.

Suppose we return the sunshine to the sun. Do you think that this sheet of paper would be possible? No, without sunshine nothing can be. And if we return the logger to his mother, then we have no sheet of paper either. The fact is that this sheet of paper is made up only of “non-paper elements.” And if we return these non-paper elements to their sources, then there can be no paper at all. Without non-paper elements, like mind, logger, sunshine, and so on, there will be no paper. As thin as this sheet of paper is, it contains everything in the universe in it.

Everything is connected not by consciousness, but rather by inter-dependency. It's a great explanation on conditioned things, sankhara.

The rest of the article explains Mahayana Emptiness.